Vision-Based Interfaces for Character-Based Text Entry: Comparison of Errors and Error Correction Properties of Eye Typing and Head Typing

Table 4

Characteristics of gaze- and head-based VBIs for hands-free text entry.

Eye typing	Head typing
Pros	Pros
Fast speed of text production (efficiency)	Possibility to freely observe text and keyboard layout
Easiness-of-use/less physical effort if large (1.5–2°) keys are used (efficiency)	Small number of errors (effectiveness) and small number of error corrections (efficiency)
Text entry is possible even for severely disabled users	Does not require extensive learning for error-free performance; Can be used with small (0.4°) keys [28]; Lower error correction cost (when the error rate is small)
Cons	Cons
Gaze is tied to the typing task itself	Slow speed of text entry
Requires large keys (and a keyboard takes large screen space)	Requires that control over head (and may be even torso) motion is preserved
Eye fatigue in case of small keys [28]	Physical fatigue
Requires learning for error-free performance
Higher error correction cost (when the error rate is small)